I found this cool tool that can help you figure out how far you've walked or run when you decide to take it outside for a little fresh air. Alternatively you can have a distance goal in mind and start drawing on the map to figure out where you should go to meet your distance goal.
Here is a sample route from my house. I found the interface a little tricky at first, but if you just make small clicks along the route you want, it will draw the line for you.
P.S.- I realize Nike has similar functionality on their site so if that one already works for you keep on keepin' on. If you haven't tried the Nike one, hopefully this post will give you some incentive. If you don't have or want to get a Nike login, then try the mapmyrun one out. They're all powered by google anyway, lol.